Dark Skies

When the New Yorker isn't pushing a political agenda, they often write well-written, thoughtful articles like this one from the August 20, 2007 issue about the importance of dark skies:

In 1610, Galileo Galilei published a small book describing astronomical observations that he had made of the skies above Padua. His homemade telescopes had less magnifying and resolving power than most beginners’ telescopes sold today, yet with them he made astonishing discoveries: that the moon has mountains and other topographical features; that Jupiter is orbited by satellites, which he called planets; and that the Milky Way is made up of individual stars. It may seem strange that this last observation could have surprised anyone, but in Galileo’s time people assumed that the Milky Way must be some kind of continuous substance. It truly resembled a streak of spilled liquid—our word “galaxy” comes from the Greek for milk—and it was so bright that it cast shadows on the ground (as did Jupiter and Venus). Today, by contrast, most Americans are unable to see the Milky Way in the sky above the place where they live, and those who can see it are sometimes baffled by its name.

The stars have not become dimmer; rather, the Earth has become vastly brighter, so that celestial objects are harder to see. Air pollution has made the atmosphere less transparent and more reflective, and high levels of terrestrial illumination have washed out the stars overhead—a phenomenon called “sky glow.” Anyone who has flown across the country on a clear night has seen the landscape ablaze with artificial lights, especially in urban areas. Today, a person standing on the observation deck of the Empire State Building on a cloudless night would be unable to discern much more than the moon, the brighter planets, and a handful of very bright stars—less than one per cent of what Galileo would have been able to see without a telescope.

The article also points to a curious and disturbing correlation--one that I have seen mentioned before, but I am still skeptical of, but weirder things than this have to turned to be true:

The twenty-four-hour day/night cycle, which is also known as the circadian clock, influences physiological processes in virtually all living things. Pervasive artificial illumination has existed for such a brief period that not even the species that invented it has had time to adapt, biologically or otherwise. The most widely discussed human malady related to the disturbance of circadian rhythms is jet lag, but there are others. Richard Stevens, a cancer epidemiologist at the University of Connecticut Health Center, in Farmington, has suggested a link between cancer and the “circadian disruption” of hormones caused by artificial lighting. Early in his career, Stevens was one of many researchers struck by the markedly high incidence of breast cancer among women in the industrialized world, in comparison with those in developing countries, and he at first supported the most common early hypothesis, which was that the cause must be dietary. Yet repeated studies found no clear link to food. In the early eighties, Stevens told me recently, “I literally woke up in the middle of the night—there was a street lamp outside the window, and it was so bright that I could almost read in my bedroom—and I thought, Could it be that?” A few years later, he persuaded the authors of the Nurses’ Health Study, one of the largest and most rigorous investigations of women’s medical issues ever undertaken, to add questions about nighttime employment, and the study subsequently revealed a strong association between working the night shift and an increased risk of breast cancer. Eva Schernhammer, of the Harvard Medical School, and Karl Schulmeister, an Austrian physicist, analyzed the work-shift data from the Nurses’ Study several years ago, and wrote, “We hypothesize that the potential primary culprit for this observed association is the lack of melatonin, a cancer-protective agent whose production is severely diminished in people exposed to light at night.”

The article also points out the obvious environmental benefits--but points out that environmentalists haven't been much concerned about this:

Although nighttime lighting has seldom been a priority of environmentalists—one of whom described it to me recently as a “soft” issue—bad or unnecessary lighting not only wastes billions of dollars’ worth of energy every year but also can wreak havoc on ecosystems. Migrating birds can be fatally “captured” by artificial lights, a fact that was made obvious a half century ago, when early versions of a common meteorological device called a ceilometer—which used a powerful vertical beam of light to measure cloud ceilings—sometimes killed thousands of migrating birds in a single night. Artificial light can be especially lethal to insects. Gerhard Eisenbeis, a German entomologist, has written that outdoor lighting can have a “vacuum cleaner” effect on local insect populations, causing large numbers to be “sucked out of habitat.” An earlier German study showed that new, brightly lit gas stations initially attracted large numbers of insects, but that the numbers fell rapidly after two years, presumably because local populations were decimated. One of the several ways in which light fixtures kill insects is by causing them to rest on the ground or in vegetation, where they become easy prey.

This essay is well worth reading in full for the pleasure of its writing. Time to annoy my county commissioners about the subject, I suppose.